Cranes are often used in the marine environment for the purposes of lifting objects or for the purposes of placing objects from one position to another. The cranes are often used in offshore operations, such as drilling rigs, ships, and loading facilities. In nearly all applications, cranes typically includes a boom which extends outwardly from a platform, a lifting line extending along the boom, and a load block which is received at the end of the line. A hook is positioned at the bottom of the load block so as to facilitate the lifting and lowering activities of the crane.
FIG. 1 shows a conventional prior art application of a load block 2. As can be seen, the load block 2 is affixed to the end of a line 4 extending from the winch 6 of the crane 7. A boom 8 extends outwardly from the platform 9. As shown in FIG. 1, the lifting device is a lifting system on a railroad line. In normal use, the load block 2 will include at least one sheave which allows the line 4 to extend therearound. Quite commonly, the load block 2 will include a plurality of sheaves so as to facilitate the lifting and weight requirements of the winch 6 of the crane 7. Normally, the line will extend around the sheaves in a predetermined manner so as to reduce the lifting forces. One end of the line 4 is shown as affixed to a surface of the boom 8 of the crane 7. This end of the line 4 will remain fixed during the lifting and lowering activities of the load block 2. When it is desired to lift the load block 2, then the winch 6 will rotate so as to pull in the line 4. If it is desired to lower the load block 2, then the winch 6 will reel out the line 4 so that the load block 2 is lowered. The sheaves within the interior of load block 2 continually roll relative to the movement of the line 4.
In normal onshore uses, the load block 2 should last for an indefinite period of time. The load block 2 includes a steel body, contains sheaves rotatably positioned within the body, and has a hook extending outwardly from a bottom of the body. Normally, the hook will have a threaded shank. A nut is positioned around the threaded shank so as to retain the hook in a proper position extending outwardly of the bottom of the body of the load block 2.
Unfortunately, in marine applications, the load block 2 is subjected to a large number of corrosive actions. For example, the load block 2 is constantly affected by sea water. As a result, rules have come into effect that require the periodic inspection of these load blocks. Since the load blocks are utilized in the lifting of large weights, it can often be dangerous if the load block is sufficiently corroded that a failure of the load block occurs. These failures can often occur in the joining of the shank to the body of the load block or in the shaft which is used to support the sheaves of the load block. A great deal of personal injury litigation has resulted, in the past, over the failure of such load blocks in the marine environment.
Although the requirements of the marine environment dictate that a different type of load block 2 be used then that used in conjunction with the railroad car shown in FIG. 1, it is virtually always the case that the offshore operators will utilize similar load blocks. As a result, the load blocks will become quickly corroded during their use in the offshore environment. Corrosion of the load blocks makes inspection difficult or nearly impossible. Often, if inspection is impossible, the load block must be replaced by a properly inspected and approved load block. The replacement of these load blocks can be very expensive to the operator. In certain circumstances, the load block can be so corroded that it will result in catastrophic failure. In other circumstances, the load block will corrode or deteriorate to the point that it no longer functions effectively as a load block.
It is an object of the present invention to provide a load block that is resistive of the elements in the marine environment.
It is another object of the present invention to provide a load block that facilitates the inspection and/or repair of the load block.
It is a further object of the present invention to provide a load block that facilitates the reeving of the load block.
It is a further object of the present invention to provide a load block that offers improved strength, stability, and safety.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.